Blood viscosity is lower in trained than in sedentary sickle cell trait carriers.

The aim of this study was to compare blood and plasma viscosities, as well as the hematocrit/blood viscosity ratio (HVR), between trained and sedentary SCT carriers. Thirty African male SCT carriers from the city of Dakar (Senegal) participated in the study: one group composed of 15 trained SCT carriers (TSCTc) and one group composed of 15 sedentary individuals (SSCTc). Blood was sampled in resting condition and blood and plasma viscosities were measured using a cone-plate viscometer. After the determination of hematocrit by microcentrifugation, HVR was determined for each subject. Blood and plasma viscosities, as well as hematocrit, were significantly reduced in TSCTc compared to SSCTc. As a consequence, HRV was greater in TSCTc. These findings provide evidence that SCT carriers should be encouraged to practice regular physical activity to limit the cardiovascular strain usually caused by their blood hyperviscosity.